UPDATE JULY 26, 2013: George Mitchell died at the age of 94 on Friday. The profile below was based on one of the final public interviews he gave.

He cracked the code. That's what folks in the oilpatch say about George Mitchell. In the 1970s and '80s, the country's conventional, big pools of natural gas were tapped out. Drillers looked in new geologic formations, but found themselves stumped.

"We knew the gas was there," Mitchell tells Marketplace. "We didn't know how to get it free."

Now 93, this is likely Mitchell's last interview. We spoke at a hotel he owns in his hometown, Galveston. The billionaire Mitchell -- son of a Greek immigrant, real-estate developer, environmental philanthropist -- is by all accounts an independent, stubborn soul.

His firm's breakthrough was coaxing natural gas from stubborn rock known as shale. It unlocked a new geologic door to fossil energy. The innovation of shale fracking has tongues wagging about U.S. energy security, creating millions of new jobs, and eviscerating America's trade deficit. Perhaps.

"Mitchell is really the giant here," says Diana Davids Hinton of the University of Texas-Midland. "In terms of the recent industry, George Mitchell's significance is both national and global. What his work did opened up possibilities that are mind-boggling."

Mitchell began poking in shale in the early '80s, in a picked-over spot in east Texas called the Barnett Shale. Shale is dense, tight rock that traps hydrocarbons inside. Back in the day, some even even pondered exploding atom bombs underground to get the energy out.

Most drillers sniffed and walked away.

"I've had a lot of engineers and geologists say, you're wasting your money, Mitchell," Mitchell says. "We knew enough to go on and keep doing it, because we saw we were making progress."

Not that his staff was always convinced. Geologist Dan Steward, now at Republic Energy, worked for Mitchell then. He recalls shutting down what he and his colleagues considered an unpromising well. A dog, as they say.

"And George said, 'okay let me get this right.'" Steward says. "'We drilled this well to understand an objective we don't understand. And we plug the well without evaluating it? What were you thinking? What were you drinking? What were you smoking?' And he wasn't quite that nice."

In 1982, Mitchell gave his staff a deadline: produce shale gas in 10 years, or the company's in trouble.

"He says if y'all -- if you team -- don't think you're up to this challenge, let me know. I'll find people who are," Steward says. "I had a wife and four kids, I said 'we can do it, boss!'"

"When you had an up you thought Ooh, we've got it now," Steward says. "But then, two weeks from now you'd have this down and you'd say, what the hell?"

Eventually, Steward's team discovered the key to recovering natural gas was cracks in the shale. Thing is, they had to manufacture new cracks to get it out – like hitting a windshield with a baseball bat. In this case, the bat is high-pressure fluid, shot down hole to fracture – or frac – the shale rock.

Contrary to what some believe, fracking is not a new technology. It's been around since the late 1940s. But Mitchell Energy tweaked it for shale, with much frustration. They tried various chemicals, gels and various combinations and frac juice recipes. One frustrated staffer suggested a horse manure frac.

"That's a pretty good quote," Mitchell recalls. "We were discouraged we weren't getting good results. And we had tried all other types of fracs.

By the mid 90s, money at Mitchell Energy was tight. Each well cost upwards of a million dollars to drill and frac. One worker suggested a budget frac, of mostly water instead of an expensive gel-based fluid. That raised eyebrows. Water tends to swell rock, shrinking the valuable fractures. But Mitchell Energy gave it a shot.

"Conventional wisdom was wrong," says company alum and Houston-area geologist Kent Bowker. "We want low viscosity fluid. We want water and that was an eye opener."

Turned out, water saved money. And in a surprise finding, it yielded more gas.

Luck has played a starring role in many innovation stories. The discovery of penicillin. And the development of a drug originally meant for heart disease, until researchers stumbled upon a different use: the drug Viagra.

Kent Bowker played a key role in a second Eureka moment. In the late 90s, he had a hunch the Barnett held more gas than the company assumed. Bowker just needed money to test it out. Company president Bill Stevens said no.

"He physically stuck his hand in my face and said, 'stop right there. We have enough of that stuff,'" Bowker says. "Bill Stevens never believed in it. He would go on CNBC and call it black tombstone."

But founder and CEO George Mitchell blessed Kent Bowker's science experiment. Its finding: the ground below held four times the gas they figured. Meeting time.

"And Mitchell got a big smile on his face," Bowker says. "He leans forward and says, 'This is huge! This is the biggest thing that's ever happened at this company. It's also the biggest secret, no one can say anything about this.'"

"I remember the meeting," Mitchell says. "Of course I didn't want him to tell anyone. The Barnett was a very big reservoir. And therefore if we could make it work, it could be very profitable.

Mitchell Energy poured money into drilling wells much more closely together than before. With the new information, they'd discovered the keys to making Barnett Shale wells moneymaking and commercial. They'd cracked the code.

Of course it did take 17 years to get there, not exactly your overnight wonder. Breakthroughs often take time.

"That's true with almost every major commercially viable innovation I can think of," says Harvard Business professor Teresa Amabile. She cites the example of the Kindle Reader.

"The initial insight for electronic ink occurred to a scientist named Joe Jacobson in 1995," Amabile says. "While he was lying on a beach in California. Look how many years it took to come up with a good color electronic ink that is commercially viable and useful."

The lesson she draws is, keep persisting. And keep ... failing.

"There are more and more failures than there are successes in most innovation journeys. What you need to do is figure out how to extract failure value. Figure out what you can learn from what went wrong.

Today, shale fracking technology is widespread, and still evolving. Another company, Devon Energy, paired fracking with horizontal sideways drilling, another breakthrough that yields even more gas. There's fracking for shale oil, variations known as simul-fracking and zipper fracking.

The point is, additional innovations keep coming. To many, shale is still at a nascent state of development: think initial, chunky, $800 cell phone.

"The level of the intelligence is very low," says Nansen Saleri of Quantum Reservoir Impact, a former top manager at the Saudi national oil company. He thinks the level of shale IQ will double or triple in the coming decades, at which point people will look back at today as "the initial dinosaurish phase of shale and unconventional resource development."

Of course, innovation is one thing. Whether it's good for society is quite another. And, like nuclear energy and genetic engineering, fracking draws critics, fearful of the drilling effects on drinking water, and the carbon emissions implications.

"That's going to prolong our dependence on the fossil fuel industry," Emily Wurth at Food and Water Watch. "Which is in their best interest, at a time when we need to be aggressively moving away from using fossil fuels."

Mitchell's view on that is a bit of a twist. He supports fossil fuel taxes, which could phase out his discovery. And his foundation has given millions to research clean energy.

"I've had too much experience running independents," Mitchell says. "They're wild people. You just can't control them. And if it doesn't do it right, penalize the oil and gas people. Get tough with them."

The words of a Texas oilman, talking out of school. It's not the first time George Mitchell has turned an idea upside down. And now, his breakthrough has turned America's fossil fuel debate on its head -- from one of scarcity to one of abundance.